Though the entire set of browser versions are developmental at present, a straight "TP" version is considered the most stable and least experimental. The 'team blog' Snapshot versions are the most up-to-date in terms of features and fixes, but the new features beyond the TP version can introduce their own sets of problems. That said and given that everything is still a work much in progress, most users, as @Pesala notes, will find that using the latest Snapshot will present the fewest significant issues - particularly when the latest TP version has become several months old.

Eventually, after the browser is someday formally 'released', the latest stable, released version will replace the TP version placeholder and the Snapshot versions will become the more formalized alpha and/or beta versions… but that day has not yet arrived. Everything is still essentially alpha in nature.

Well, after some years, I recently found out about Vivaldi. I had to install it straight away.
I am still using Opera, but straight out of the box I can tell…it's like seeing an old faithful friend again you haven't seen in a while. Love it already and I have installed it 45min ago.
So, thank you for keeping the spirit of the original Opera alive. It is really a pleasure to have the functionality back again.

The only thing I can see missing at the moment is the bottom pop-up loading bar, but I guess at the speeds we are talking in this age, it's sort of useless now. So I'm ok with it.

Well, after some years, I recently found out about Vivaldi. I had to install it straight away.
I am still using Opera, but straight out of the box I can tell…it's like seeing an old faithful friend again you haven't seen in a while. Love it already and I have installed it 45min ago.
So, thank you for keeping the spirit of the original Opera alive. It is really a pleasure to have the functionality back again.

The only thing I can see missing at the moment is the bottom pop-up loading bar, but I guess at the speeds we are talking in this age, it's sort of useless now. So I'm ok with it.

Welcome! If you have just installed the TP4 from the front page of Vivaldi.com, you may want to try the current snapshot from https://vivaldi.net/ !! There have been seventeen updates and many advancements since the Technical Preview!